$ perl -e '$s="JustAnotherPerlHacker\n"; $s=~s/(?<=.)(?=[A-Z])/ /g; print $s'
Just Another Perl Hacker

##</code><code>##

$s=~s/(?<=\S)(?=[[:upper:]])/ /g

##</code><code>##

$ perl -e '$s="JustAnotherPerlHacker\n"; @a = split /(?<=\S)(?=[[:upper:]])/, $s; print "@a"'
Just Another Perl Hacker